PLCs and SCADA Systems — MCQs – EE

1. What does PLC stand for?
(A) Programmable Logic Controller
(B) Process Logic Computer
(C) Power Line Controller
(D) Programmable Load Control

2. What does SCADA stand for?
(A) Supervisory Control and Data Acquisition
(B) System Control and Direct Access
(C) Sequential Control and Data Application
(D) Smart Control and Data Analysis

3. A PLC is primarily used for:
(A) Automation and control of industrial processes
(B) Data storage
(C) Electrical power generation
(D) Signal transmission

4. The main components of a PLC are:
(A) CPU, Memory, Input/Output modules, Power supply
(B) CPU, Modem, Battery, Speaker
(C) Transmitter, Receiver, Antenna
(D) Keyboard, Monitor, Printer

5. The CPU in a PLC performs:
(A) Processing and control operations
(B) Signal amplification
(C) Mechanical actuation
(D) Power generation

6. Inputs to a PLC are typically from:
(A) Sensors and switches
(B) Motors
(C) Actuators
(D) Displays

7. Outputs from a PLC are typically connected to:
(A) Actuators and indicators
(B) Sensors
(C) Transmitters
(D) Receivers

8. The programming language commonly used in PLCs is:
(A) Ladder Logic
(B) Assembly Language
(C) Python
(D) HTML

9. The ladder diagram in PLC programming resembles:
(A) Electrical relay logic
(B) Flowchart
(C) Block diagram
(D) Circuit breaker diagram

10. In PLCs, scan time refers to:
(A) Time taken to complete one cycle of reading inputs, executing logic, and updating outputs
(B) Time taken to upload a program
(C) Communication delay in network
(D) Power-up delay

11. Which memory type stores the PLC program?
(A) EEPROM or Flash Memory
(B) RAM only
(C) Cache Memory
(D) External Hard Drive

12. A digital input in a PLC can detect:
(A) ON or OFF status
(B) Analog voltage levels
(C) Variable frequency
(D) Temperature variation

13. An analog input module in PLC is used to measure:
(A) Continuous signals like temperature or pressure
(B) Binary signals
(C) Logic levels
(D) Pulse signals only

14. The watchdog timer in a PLC ensures:
(A) System reliability and fault detection
(B) Communication speed
(C) Memory optimization
(D) Power control

15. In SCADA, the RTU stands for:
(A) Remote Terminal Unit
(B) Real Time Unit
(C) Remote Transmitting Unit
(D) Reactive Timing Unit

16. The HMI in a SCADA system refers to:
(A) Human-Machine Interface
(B) Hardware Monitoring Interface
(C) Host Machine Input
(D) High Memory Interface

17. The main purpose of SCADA is:
(A) Monitoring and controlling industrial processes remotely
(B) Data encryption
(C) Hardware troubleshooting
(D) Voltage regulation

18. SCADA systems collect data from:
(A) Sensors and field devices
(B) Servers
(C) Relays only
(D) Network switches

19. Communication between PLC and SCADA is done via:
(A) Industrial communication protocols
(B) Telephone line
(C) Audio signals
(D) Manual entry

20. Common communication protocols in PLC-SCADA systems include:
(A) Modbus, Profibus, Ethernet/IP
(B) HTTP, SMTP, FTP
(C) Bluetooth, Wi-Fi, NFC
(D) PCI, ISA, AGP

21. The Master Terminal Unit (MTU) in SCADA performs:
(A) Central control and data processing
(B) Field data measurement
(C) Signal amplification
(D) Local switching

22. The RTU in SCADA connects to:
(A) Sensors and actuators in the field
(B) Computers in the control room only
(C) Servers only
(D) Power supplies

23. PLCs are widely used in:
(A) Industrial automation and process control
(B) Web design
(C) Office management
(D) Data entry

24. SCADA systems are typically used for:
(A) Large-scale process monitoring
(B) Small circuit switching
(C) Local relay control
(D) Power backup

25. A redundant SCADA system ensures:
(A) High reliability and fault tolerance
(B) Lower power usage
(C) Faster network speed
(D) Smaller system size

26. The PLC I/O module converts:
(A) Field signals to logic levels and vice versa
(B) Digital to audio
(C) Text to binary
(D) Voltage to frequency

27. The analog output of a PLC is used to:
(A) Control variable devices like valves or drives
(B) Turn relays ON or OFF
(C) Transmit digital codes
(D) Drive LED indicators only

28. SCADA systems use data logging to:
(A) Record process data for analysis and troubleshooting
(B) Control actuators directly
(C) Reset PLC programs
(D) Increase data transmission speed

29. A PLC network can be connected using:
(A) Ethernet, RS-485, or Fieldbus
(B) Coaxial cable only
(C) Fiber optics only
(D) USB only

30. The major advantage of PLC and SCADA integration is:
(A) Real-time monitoring and automatic control of industrial systems
(B) Manual process handling
(C) Increased human supervision
(D) Reduced communication speed